The endpoints of a line segment are (2, 3) and (8, 15). What is the sum of the coordinates of the midpoint of the segment?
The midpoint of a line segment with endpoints $(x_1, y_1), (x_2, y_2)$ is $\left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right)$.

Thus, the midpoint of this line segment is $\left(\frac{2+8}{2}, \frac{3+15}{2} \right)$, which simplifies to $(5,9)$. Thus, the sum of the coordinates of the midpoint is $\boxed{14}$.